CI: Move all ubuntu-18.04 to ubuntu-20.04

[deepthi]

Description

Ideally we should run on ubuntu-latest but let's see if this works first.

Related Issue(s)

Checklist

• "Backport me!" label has been added if this change should be backported
• Tests were added or are not required
• Documentation was added or is not required

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[vitess-bot]

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[dbussink]

Ideally we should run on ubuntu-latest but let's see if this works first.

Probably good to define a specific version so we don't have to scramble if Actions changes ubuntu-latest. Fwiw, ubuntu-latest still points at 20.04 anyway and not at 22.04.

With 22.04 there's also other issues like it ships with OpenSSL 3.0 and only MySQL 8.0.30 has support for that. I guess binary packages might have those fixes backported by maintainers but it might be a friction point there. I also don't know if MySQL 5.7 would ever see OpenSSL 3.0 support so we might be stuck there with an older base for CI anyway.

[dbussink]

Hmm, is the xtrabackup related issue that we've upgraded it also for MySQL 5.7 but we now get a version there that's doesn't work with 5.7? Since we already seemed to have MySQL 8.0 running against 20.04 if I read the diff right?

[dbussink]

We also seem to have some other stuff that might now run against MySQL 8.0 and not 5.7?

--- FAIL: TestSchemaVersioning (0.25s)
[325](https://github.com/vitessio/vitess/runs/7952828721?check_suite_focus=true#step:11:326)
    vstreamer_test.go:169: insert into vitess_version values(1, 10) (0): event:
[326](https://github.com/vitessio/vitess/runs/7952828721?check_suite_focus=true#step:11:327)
        "type:FIELD field_event:{table_name:\"vitess_version\" fields:{name:\"id1\" type:INT32 table:\"vitess_version\" org_table:\"vitess_version\" database:\"vttest\" org_name:\"id1\" column_length:11 charset:63 column_type:\"int\"} fields:{name:\"id2\" type:INT32 table:\"vitess_version\" org_table:\"vitess_version\" database:\"vttest\" org_name:\"id2\" column_length:11 charset:63 column_type:\"int\"}}", want
[327](https://github.com/vitessio/vitess/runs/7952828721?check_suite_focus=true#step:11:328)
        "type:FIELD field_event:{table_name:\"vitess_version\" fields:{name:\"id1\" type:INT32 table:\"vitess_version\" org_table:\"vitess_version\" database:\"vttest\" org_name:\"id1\" column_length:11 charset:63 column_type:\"int(11)\"} fields:{name:\"id2\" type:INT32 table:\"vitess_version\" org_table:\"vitess_version\" database:\"vttest\" org_name:\"id2\" column_length:11 charset:63 column_type:\"int(11)\"}}"
[328](https://github.com/vitessio/vitess/runs/7952828721?check_suite_focus=true#step:11:329)
FAIL

That looks very much like an issue where on MySQL 5.7 integer lengths are still printed for a schema, but that doesn't happen anymore for MySQL 8.0.

[deepthi]

Some parts of this have already been picked out and merged, and #11153 handles the rest. Hence, closing.